Structural biology of type VI secretion systems

Area of Science:

• Microbiology
• Structural Biology
• Molecular Biology

Background:

• Type VI secretion systems (T6SSs) are essential bacterial protein transporters.
• TSSs mediate interactions with host cells or other bacteria, impacting pathogenesis and niche colonization.
• The assembly mechanisms of these complex transenvelope structures remain largely unknown.

Purpose of the Study:

• To review recent structural findings on individual T6SS components.
• To emphasize the composite nature of T6SSs, integrating subunits from various sources.
• To provide insights into the assembly of these intricate molecular machines.

Main Methods:

• Literature review of recent structural studies on T6SS components.
• Analysis of protein domain origins and evolutionary adaptation.
• Integration of structural data to propose assembly models.

Main Results:

• T6SSs are composite systems, assembling from distinct protein modules.
• One module resembles contractile bacteriophage tails.
• Other subunits are embedded in the inner and outer membranes, anchoring the system.

Conclusions:

• T6SSs are sophisticated molecular machines with a modular architecture.
• Understanding the structural basis of T6SS assembly is crucial for deciphering their function.
• The adaptation of subunits from diverse origins highlights evolutionary flexibility in secretion system development.